Well... nothing... because nobody will tell you otherwise, at least not in Britain:

The word "fail" should be banned from use in British classrooms and replaced with the phrase "deferred success" to avoid demoralizing pupils, a group of teachers has proposed.

Members of the Professional Association of Teachers (PAT) argue that telling pupils they have failed can put them off learning for life.

Now how can you argue with logic like that? The PAT also promised that if the ban were to take effect, they would revisit the issue in a few years to see if their student's success in life had been deferred due to such idiotic ideas.